Electrical circuit breaker



July 17, 1951 H. w. KOCH 2,560,800

ELECTRICAL CIRCUIT BREAKER Filed Dec. 31, 1947 M/Vf/VTOR H. W KOCH Patented July 17, 1951 UNITED STATES PATENT OFFICE ELECTRICAL CIRCUIT BREAKER Herbert W. Koch, Cicero, 1ll., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application December 31, 1947, Serial No. 794,972

2 Claims. 1

This invention relates to electrical circuit breakers and more particularly to a protective circuit breaker for an electrical line.

It is an object of this invention to provide a new and efficient circuit breaker for electric lines.

In accordance with one embodiment of this invention an apparatus for protecting an electrical line against overloads and short circuits is provided with switching contacts for opening and closing the line, the contacts being held closed under normal conditions by a normally operated parallel relay connected across the load through the closed break contacts of a normally unoperated relay connected in series with the load. In case of an overload, the series relay operates to release the other relay thereby breaking the line, thus releasing the series relay and again operating the other relay to close the line. This cycle keeps repeating itself until the line is relieved of the overload. In case of a short circuit in the line, the shunt eliect of the short around the parallel relay causes the current through the parallel relay to drop to immediately release the relay and open the line thus removing the direct shunt from across the parallel relay permitting it to reoperate, the cycle being repeated until the short circuit is removed.

A complete understanding of this invention will be had by referring to the following detailed description taken in conjunction with the single figure drawing in which one embodiment of the invention is illustrated by a circuit diagram.

As shown in the drawing, a circuit breaking apparatus comprising relays I and II is utilized to protect an electrical circuit comprising a source of electrical energy I2 connected to a load I3 through electrical lines I4 and I5.

The relay I0 which is normally unoperated comprises an operating coil 2| connected in the line I5 in series with the load l3 and a pair of normally closed break contacts 20. The relay I I is normally operated and is provided with a pair of normally closed make contacts 22 and an operating coil 23 having one end connected to the line I4, the other end of the coil being normally connected to the line I 5 through the closed contacts 20; thus while the relay I0 is connected in series with the load I3, the relay I I is normally connected across the lines I4 and I5 and in parallel with the load I3.

The contacts 22 serve as a switch in the line I 4 and operate to break the line circuit when the relay coil 23 is deenergized. Excessive arcing between the contacts 22 may be prevented by connecting a resistor 24 across the contacts as shown in the drawing. A lamp 25 may be connected to the lines I4 and I5 in parallel with the load I3 to indicate the condition of the circuit. The operating characteristics of the relay II are such that under normal load conditions the break contacts 20 remain closed due to the fact that the current through the operating coil 2I will be insufficient to operate the relay I0. However, if there is an increase in the load I3 beyond predetermined safe limits, the relay I0 will be operated by the increased current through its operating coil 2|, thereby breaking the contacts 20 and releasing the relay II. Upon release of the relay II, the contacts 22 are opened, and the direct line circuit I4 to the load I3 is broken. The resistor 24 remains in the circuit but its resistance should be high enough to limit the current below the value required to operate relay I I]. When the line circuit I4 is broken at opened contacts 22, the relay I0 is released to close contacts 20 thereby reoperating relay I I and again closing the line at the contacts 22. This causes relay II! to operate again thereby releasing relay I I to again open the line at contacts 22. This cycle is repeated until the load I3 is reduced to normal, whereupon relay III will be unoperated and relay I I will be operated to maintain the line circuits at contacts 22. While the line is intermittently opened and closed at contacts 22 during the period of the overload, the normally lighted lamp 25 will flicker to provide a visible danger signal.

The design and the type of relays chosen are dependent upon the timing relation desired for a particular case. The timing relation may be such as to provide a short on time and a long "ofl time during the overload or vice versa.

Preferably the relay I I has a fast release time as compared to the operate time of the relay III. A short circuit or a near short circuit in the load I3 will cause the relay II to rel-ease before the relay I0 can operate thereby breaking the line circuit at the contacts 22. This is due to the fact that the short circuit in the load forms a direct shunt across the relay II and drops the current through the relay. Breaking of the line circuit at contacts 22 removes the direct shunt from across relay II thereby permitting it to reoperate to again close the line at contacts 22. This cycle is repeated until the short circuit is removed, after which the line circuit to the load is restored. The indicator lamp 25 will flicker while the short circuit exists.

The average power consumed during an overload when this circuit breaking apparatus is used *will be lower than that consumed by a conventional circuit breaker, especially if the on time 40f contacts 22 is a relatively short part of the time -of the make and break cycle during the overload period. The apparatus described herein will, with :a minimum of power drawn from the line, inter- ;mittently break an overload or shorted electrical power line until the line is relieved of the overload :and then restore the line circuit when the overload or short circuit is removed. It is to be understood that the above-described arrangements are simply illustrative of the appli cation of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within th .spirit and scope thereof.

What is claimed is: l. A circuit breaking apparatus comprising a :source of current, a load connected to said source, a normally unoperated first relay with normally closed break contacts, said relay havingan operating coil connected in series with said source and said load and being unoperative under normal loads, a normally operated second relay' having an operating time less than said first relay con nected across said load through said'break contacts, said second relay having" normally closed make contacts and operable upon release to open and break the circuit between the source of current and the load, said second relay being deenergized before operation of said first relay when a short circuit occurs in said load so that increased protection is afiorded under short circuit conditions. 7

2. A circuit breaking apparatus comprising a source of current, a load. connected to said source, a normally unoperated first relay with normally closed break contacts, said relay having an oper: ating coil connected in series with said source and said load and being unoperative under normal loads, a normally operated second relay having an operating time less than said first relay connected across said load through said break contacts, said second relay having normally closed make contacts and intermittently operated upon release to open and break the circuit between the source of current and the load when the current to said load exceeds a predetermined value, said intermittent operation enabling said first and second relays to immediately resume normal operating conditions when the current falls below said predetermined value, said second relay being ole-energized before operation of said first relay when a short circuit occurs in the load so that increased protection is afforded under short circuit conditions.

HERBERT W. KOCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date ZBBAGO Sawyer Jan. 11, 1881 836,279 Schneider Nov. 20, 1906 913,43? Schoeller Feb. 23, 1909 957,334 Henderson May 10, 1910 1,101,495 Kraemer w June 23, 1914 1,112,639 Miller Oct. 6, 1914 1,214,101 Wessel Jan. 30, 1917 1,270,785 Chubb July 2, 1918 1,296,314 Pettersen Mar. 4, 1919 1,328,457 Sancorn Jan. '20, 1920 1,339,456 ienderson May 11, 1920 1,513,247 James Oct. 28, 1924 1,652,346 Burnham Dec. 13, 1927 1,725,022 Stacy et a1 Aug. 20, 1929 1,871,875 Bradford Aug. 16, 1932 FOREIGN PATENTS Number Country Date 8,225 Great Britain Feb. 9, 1911 61,777 Switzerland June 18, 1912 

